The invention relates to trunked radio communication systems. Specifically this invention provides a method and apparatus for allowing automatic system resource acquisition by utilizing dual system resource listings when monitoring priority communications within a particular geographic communication coverage area.
Trunked communication systems provide an efficient use of limited frequency spectrum. In a trunked communication system a primary communication control resource (PCCR) allocates a limited number of system resources among many communication units (CUs). System resources are typically RF (ratio frequency) channels such as frequencies, frequency pairs, or TDM time slots. The PCCR continuously sends an outbound signalling word (OSW) stream to the CUs, and a CU sends an inbound signaling word (ISW) to the PCCR when a system resource is desired. Since the number of system resources is far less than the number of CUs, the PCCR typically monitors previously assigned resources. When a system resource remains unused for a predetermined period of time, the PCCR typically makes the system resource available for use by other CUs.
In the past, a system resource has been available from a control resource's single listing. To provide for a functional priority monitoring system, typically an alarm system, manual input from the priority monitoring system is transmitted to control resource, and the control resource, when desired, alerts a CU as to the priority monitoring system status. In this way CUs are alerted to an alarm type and location. Such a procedure does not allow for integration of a control resource based communication system and a priority monitoring system. A need exists for integrating priority monitoring reporting into a single trunked communication system, thus reducing total cost and complexity.